Field of the Invention
The present invention mainly relates to a configuration of an automatic steering device that is mounted on a movable body, such as a ship, etc.
Background Information
Ships during navigation are affected by external disturbances, such as waves and wind, and the posture of the hull is constantly changing. For this reason, in order to maintain a constant course (the direction in which the bow of the boat points), continuing to finely operate the rudder is necessary, which becomes a significant burden on the operator. Therefore, in order to automatically maintain a preset course, an automatic steering device for feedback control of the rudder is known. This kind of automatic steering device is disclosed, for example, Japanese Unexamined Patent Application Publication No. S63-20292, Japanese Patent No. 3,677,274, U.S. Pat. No. 5,235,927.
The configuration of a common automatic steering device will be explained with reference to FIG. 9. FIG. 9 shows a block diagram of an automatic steering system comprising a conventional automatic steering device 101.
This automatic steering device 101 can be attached to a hull 1 of a ship that is to be controlled. In addition to the automatic steering device 101, a steering 2 and a direction sensor 3 are provided to this hull 1.
The steering 2 comprises an appropriate rudder drive device (for example, a hydraulic cylinder, etc.) for changing the angle of the rudder (the rudder angle). The steering 2 is configured so that, when a prescribed steering command is received, the rudder angle (steering) is changed by driving the rudder drive device according to the steering command. By appropriately changing the rudder angle by driving the steering 2, the hull 1 to be controlled is turned according to necessity, and the bow (the nose) can be pointed in the desired direction. The direction sensor 3 is configured to detect the direction in which the bow of the hull 1 is facing (heading θ). Additionally, a rudder angle sensor 4 that detects the actual angle of the rudder (the actual rudder angle δr) is provided in the vicinity of the steering 2.
The actual rudder angle δr that is detected by the rudder angle sensor 4 and the heading θ detected by the direction sensor 3 are input into the automatic steering device 101. The automatic steering device 101 comprises a target course calculating unit 10, a target rudder angle calculating unit 11, and a steering command unit 12.
A set course θS that specifies the direction in which the hull 1 should progress is input into the target course calculating unit 10. This set course θS can be manually set by, for example, operating a setting knob. The target course calculating unit 10 calculates the target course θ0 based on the set course θS.
The target rudder angle calculating unit 11 calculates the target rudder angle δ, which is a rudder angle required to face the heading θ toward the target course θ0. This target rudder angle δ can be calculated with well-known control methods, such as a PID control, based on the course deviation angle Δθ, which is the difference between the target course θ0 and the heading θ, and the heading θ.
This conventional automatic steering device 101 is configured to calculate the rudder angle deviation angle Δδ, which is the difference between the target rudder angle δ and the actual rudder angle δr. The steering command unit 12 outputs a steering command to the steering 2 to drive the steering 2 so that the rudder angle deviation angle Δδ will become zero (so as to match the actual rudder angle δr and the target rudder angle δ). The steering 2 changes the rudder angle according to this steering command.
With the feedback control above, the heading θ can be turned to the set course θS by automatically correcting the rudder angle even if the posture of the hull 1 changes due to the effects of waves, wind, etc. Therefore, maintaining the course regardless of external disturbances, such as waves and wind, becomes easy, and the burden of the vessel operator can be greatly reduced.